Furnace regulation



June 30, 1925.

1,544,091 G. H. GlBSoN FU'RNACE REGULAT ION 5 Sheets-Sheet l Filed March 5, 1925 June 30, 1925. 1,544,091

G. H. GIBSON FURNAGEV REGULAT ON Filed March 5, 1925 5 Sheets-Sheet 3 Wg .ff/@n j 4/ H HK /7' Y 1. I H l l---wwmw 1 mi@ L, j L :Pi if A/ "'f/ f'lV/U J V 1L w 2 1 1 1 l /N VENTO/e A TToR/VE Y Patented June 30, 19251 UNITED STATES urERGE H. GIBSON, 0F MGNTC'LAIR, NEW JERSEY.

FURNACE REGULATION.

Application tiled March 5, 1923. Serial No. 622,391.

T 0 all 'wwm z't may conce/vt:

Be it known that I, GEORGE H. GIBSON, a citizen of the UnitedStates, and resident of Montclair, New Jersey, in the county of Essex and State of New Jersey, have invented certain new and useful improvements in Furnace Regulation, of which the following.;r is a specitication.

The general object of my present invention is to provide im roved methods of, and apparatus for reguliting combustion in furnaces which are especially' devised and adapted for use in regulating the combustion in the boiler furnaces of a power plant comprising a plurality of boiler furnaces.

A specific object of the invention is to provide a reliable and effective control sys tem for a plurality of boiler furnaces which will permit of an easy and accurate regulation of combustion conditions in each boiler furnace of a battery of such furnaces from a common switchboard or control station, and which is flexible to permit the ready maintenance of combustion conditions in one or more furnaces which are different from those maintained in other furnaces of the battery. For exam le, l advantageously make provisions wherefiy one or more of the boiler furnaces may be operated under a constant load. while the rate of combustion in each of the other boiler furnaces in serviee is varied in automatic response to fluctuations in the difference between the total boiler load and the portion of that load carried by the boilers operating at constant load.

Another specific object of the invention is to provide for maintaining a constant or manually regulable rate of combustion a boiler beinglr heated up arid which has not vet attained the working steam pressure, while automatically varying combustion in the boilers then supplving steam in response to the load on those boilers. Another s eciic object of the invention is to rovldo improved means for regulating com ustion in a furnace heated by the combustion of two fuels, one of which is supplied at a rate unich does not vary with, and is ordinarily insufiicient to satisfy the entire heat requirements of the furnace, while the other fuel is supplied as required to furnish the additional heat needed. Still anni? object Vof the invention is to pix bustion regulating preri` adapted for use Vin furnaces oeste/.i i.; combustion of powdered con.

The various features of e-y characterize my invention with artirularity in alle f and ormina a part `of For a better underslftanfiiug: tion. however. iis adi'antayfs objects attained With in; V. Ishould be had to the accolti@ ings and descriptive matt' i illustrated and described e ments of my invention,

(lf the drawings:

Fig. l is a diagrammatie of a boiler furnace control Fig. .2 is a diagrammatic of special combustion regni for a boiler furnace heated tion of rela'iveiy vatiatie agraria' .e fuels; l

Fig. 3 is a, diagram illu-'mata cation of a portion of the eine illustrated in Fig. l: and

Fig. 4 is a diagram ille!"v modication of the contro? 'fw., Fig. 1.

In the system diagramnatiw-iig; in Fig. l. each of a, plurality s? A, and A. has :ts 'valved sti-eu maar connectedto a common stt-am maro C which supplies steam through se Jamie veri out lets or supply branches f' and C* .to dit ferent steam using devices, .fismfwinted with the steam supply branch tl. is e. 'levitra il which I term a master Bow meier" the nurpose and effect of which is to maintain an electric contre? current which proper tional in strength to the rate ai .f through the supply connect devised, in my prior Patent f. and other patents and a; closed various flow met. purpose specified. The Stv grammatieally illustretfd mei a differential pressure gauge l?" of two pressure chambers sepamoid 't' flexible dia liragm or partition l toman to a lever 2 plvoted at D, and tet connections from the supply pipe C to the interiors of the pressure chambers. With this arrangement the pressure differential on the diaphragm subjects the lever D2 to a rotative impulse in the clockwise direction proportional to the dynamic pressure ot' the steam flowing through the pipe C. An opposing force is impressed on the lever D2 by the electromagnetic interaction oi' a coil D* cari ied at the upper end of the lever and stationary coils D which are connected in series in an energizing circuit including conductors 3 and 4. This circuit is energized 'from electric supply conductors or mains 1 and 2, the conductor 3 being connected to the` supply conductor 1 through the ammeter H and corresponding Switch H3. While the conductor 4 is connected to the supply conductor 2 through connections hereinafter described. Bv maintaining a constant proportion between the strength of the electric current tiowing through the coils D4 and D, and the rate of steam flow through the outlet C. the balance lever D2 may be kept in neutral position7 since the forces exerted on the lever by the current and the steam flow are proportionaL respectively. to the square of current strength and to the square of the rate of steam flow.

The electric control current flowing through the coils D* and D is automatically adjusted bv the meter D to maintain the desired ratio between its strength und the rate ot steam tlow. by means of a rheostat G to tviicl: the conductor 4 is connected. The rhcostat adiusted to vary the resistance interposed between the conductor 4 and a conductor 5 bv a reversible motor F. The latter has` one terminal connected to the suppl) conductor l through the conductor ti. and has two other terminals. one connected to a switch and the other to a "witch F," The switchesl ll and ll are so arrangcd that in thc neutral position of the ietcr W". cach switch is open. but when thc hand cud ot' the lover is raised or iowcrcd. thc y`witch Fi or the switch ll. icspectivclv. is therein.' closed. and cach ot' Altec Aifitrlus when closclh connccts4 u corrc-waulingg terminal olI the motor l" to thc l`\; conductor j through thil branch conlitt Wifi-n the switch, ll is closed. the motor l: rotates iu thc direction to dccrcasc thc boi-i n ol thc rcsistuncc of thc rhcostat (i in Matan nuit the coilsy ll and lV. and

il Viti ctt.

lblades arc in their upper nected through an arnmeter H6 to a con ductor 8 which runs to one terminal of the switch J.

Associated with the steam supply branch ('2. is a master flow meter DA which may be exactly similar in construction and oper` ation to the flow meter l). The coils D and D"I of the meter DA are connected to thc supply conductor l by a conductor 9, ammeter l'lA and switch Il, and are connected to the conductor 8 by a conductor 10. ammeter ll"` rheostat (`r.\ and conductor 11. The rhcostat GA is similar to the rheostat (i and is operated b v a motor FA similar to the motor F. and similarly controlled.

The switch J, when closed. connects the conductor 8 and thereby the conductors 5 and 11 to a bus bar or distributing conductor 12. and at vthe same time connects a cooperating bus bar 13 through a branch conductor 14 to the suppl)v conductor 2, K. K2 and K3 represent double throw switches. one for each of the boilers A. A2 and and each serving when its switch closed position, to connect the bus bats 12 and 1? through comb -tors 15 and 16, respectively. to the terminals ot' the combustion control mechanism l associated with the cortesponding boiler. '7

The purpose and etl'ect of cach device ll is to malte one or more ot' the factors controlling combustion in the corresponding boiler furnace vary in proportion to the strength of thel electric current flowing through the. corresponding c ductors 15 and 16. The factors which ay thus bc controlled include the rate of' uel supply. the rate at which air for the combustion ot' the fuel is supplied. the rate at which products of combustion are withdrawn and the combustion chamberpressure. ln my above mentioned latent 1.166,758. l have illustrated one means which mai" be employed for thus varying the supply of air to support combustioinand in my copending ap` plication. Serial No. 121.547. tiled Septembcr Q2, 1916. I have illustrated other arrangements for making a number of the combustion control factors vary in proportion to the strength of an electric current control torce. and in Fig. 2 hereof` l illustrate provisions 'for regulating various coinbustion controlling factors. A\d\'antageouslv. l include in circuit with cach pair otI conductors 15 and 11i. an individual manuall)y udiustably resistance ll. and an individual auuncter lll. and preferablyy a manually adjustable resistance tl is conucctcd in shunt to cach mechanism ll.

'ith thc switch .l closed. and one 4or more ot' thc thrce switchcaA K'. K and K ill thc position in which they connect tlu` tcrinitials otl the corresponding control mechanism ll to the bus bars 12 and li. and it llt) the hereinafter mentioned-switch L is not in its upper closed position, the aggre ate ,of the currents flowing between the bus ars `'l2 and 13 through the conductors 15 and 16 connected thereto will be pro ortional Vto the aggregate rare of steam Low through the main C through its outlets C' :and U. By' manipulating the appropriate resistances E and G, the current iow between the bus bars 12 and 13 may he divided among the different sets of local conductors 15 and 16 in any desired ratio. For instance, if .ll .three of the switches` l", K2 .and l?? have their blades in their upper closed position, equal current flows through the three control mechanisms B may be maintained, or diil'erent rates of @un rent flow through all three mechanisms B may be. maintained, or e ual current flows may be maintained `throng two of the meehaniszns l and a diii'erent current flow maintained through the third mechanism B. It the three boiler furnaces and their control mechanisms li are :ill similar in design and prtniortion, 'which may or muy not be the crine. when the control currents flowing through any two .mechanisms ll are equa the two boiler furnaces will be operated ut the saine r ting, und 'will wary the same load. lt' the boilers of ditlerent nominal ratings, but provided with similar control inecllzuiisnis B, the con-trol currents which flow through tlv-isc mechanisms must he ditlci'cn, of course, to operate the two boilers enf-h at the same per cent of' its nominal retin-1j,

To permit the operation of one or more of the boiler furnaces A', A2 and A3* at a rate which docs not fluctuate with the rate at 'which steen) is supplied througl-i the branches C and CL', I provide a second set of hns bars li" and 18 which I call the steady load bus bars. to distinguish them from the bus he und 121, which .l call the variable load luis hars. "he conductors 15 and 16 running: to any control mechanism B may be respectively connected to the bus bars 17 and 18, by throwingy the blades ot the corres onding switch K K2 or K3 into their ower closed position. "lhe bus bars 17 and 18 are connected h v conductors 190 and 195, respoctively, to the blades of a double throw switch L, which I call the steady load switch. .Advnntrigeousiy one of these conductors includes a rlicostnt G as shown. The switch L in the lower closml position of its blades connects the biz: har 1i' to the supply conductor l through conductors 19 and 190. and 'prei'erilily through un unime-ter H. and in its other closed position the switch connects the hns; har l? to the conductor l through conductor 2G. a device 57. which leali a nun. loud adjuster.y and the conductors l und lll As shown the device ijf' includes a ich lover 57 to which the conductor 20 is coniontrol nected. The lever g engages resstances gl and g'c connected, respectively, by conductors 21 and 22 tothe conductors 4 and 10, the arrangement being such that as the lever g is angularly adjusted the portion of the re sistance gb in circuit is increased, or decreased, and while the portion of the resistance g in circuit is decreased or increased. l'n each of its closed positions the switch L .serves to connect the bus bar 18 to the supply conductor 2 through the condur-tor 14.

lilith the switch blades of the switch L in their upper closed Dosition, and with the blades of the switch lx in its lower position, and with the blades of the switches K2 and K in their upper closed position, for example, the boiler A will operate with a constant rate of combustion, While the rate of combustion in the boilers A2 and A3 will vary in proportion to the variations in the difference between the total amount of steam supplied through the connections C' and C2, and the amo vit which should be generated by the boiler A". yThis follows from the fact that while the current low to the regulating.,r mechanism B of the boiler A ener ized from the steady load bus bars 17 an 18, depends on the adjustment of the manually controlled rheostats 9690, and Gl5 and on the adjustment of the resistances E and G in its local control circuit, it is not affected by the adjustments of the low meter rheosrats G and GA. inasmuch, however, as the current passing through the control mechanism B energized 'from the steady load bus bars 17 and 1S comes artly through the coils of the master How lialance D, and partly through the coils of the master flow DA, the sum of the currents flowing through the rlicoststs G and GA andthe variable load bus bars 12 and 13 will then not be proportional to the total rate of steam generation, but to the amount by which the total rate of steam generation exceeds the amount ot steam genernted by the boiler A', when o erating with the rate of combustion provide for.

While one or more of the boilers A", A and AS are being energized from the steady load bus bars 17 and 18, and one or more. are being ener (ized from the variable load bus bars 12 anI 13, if the total demand for steam falls below the output of the boilers controlled by the steady load bus bars, one or more of the boilers 'controlled from the steady load bus bars should be disconnected from the latter, and thrown over onto the variable load bus bars to avoid the generation of steam i n excess of the demand. The meter load adjuster y; is provided to vary the resul/tive no1-tions et the current supplied to rnc. constant loud bus bars-through the coils of the two master flow meters D and DA. This is desirable where the relative amounts of tenui outflow through the connections C und C2 vary from time to time, for if not provided, under some conditions the steady loud hns hars mightI druw more current through the coils ot' the flow meters D and DA connected to the outlet (7" or (if through which the smaller steum flow then passes. thun would he required to hnlnnce the lever D2 of the corresponding flow meter D or D even with the correspoi'lding rheostelt, (l or (lA adjusted to otter the maximum resistance possible to current flouv thertL through.

lVith the blades of the switch L thrown into their lower closed position. the steady loud bus lmrs li' :ind 1S ure directly energized from the supply conductors 1 und L through the conductors 14 und 19. This condition of the control circuits muy be desirulile in heatingr n hoiler up, preparatory ro putting it into operation, such-boiler hein;Y then connected to the stead)v loud hns bars. while the, boilers already in service :ire then controlled from the vuriuhle loud hus bars 12 and 13. While thel one hoiler is thus heiner tired up. u constant rute of coinhnstion will he maintained therein,4 sure :is the rute of combustion muy he lvaried by munipulution ot' the resistances (l5 und the :ippropriute resistnnees E5 and (la. It is possible also to operate :ill of the hoilers in service from the steady load hns hars 17 und 18, with the switch L in either closed position. In such case the balances D and DA ure inoperative, and I ordinarily then prefer to open the switch .l and throw the switch L into its upper closed posit-ion.

The npimrutui shown in Fig. 1 comprises provisions wherch)y the rute of combustion in tiny hoiler whether controlled from the hns hurs 12 und 18. or from the luis hors I7 :ind lr?. he nuton'mticully increased or decreased in euse the hoiler steam pressure decreases or rises :iliove the predeiermined normal stenin pressure. The provisions shown in Fig. l l'or this purpose. comprise means `for varying the electric currentI pussing;l to the, control mechanism ll of each holler from the hns hurs 1Q and, 13, or 1T nnd 1S to which the -niechunisin is connected. in response to vuriutions in the stcznn pressure. 'llic provisions shown l'or this purpose comprise shunt circuits. euch including n. conductor Ll. u conductor L'l, und more or less4 oi" :i corresponding resistance (il, con" ncrted one :across the conductors 15 und lll running to euch comhnslion control merlunisin ll. The :unonnt ot' euch ot the re sistnuces G7 thus connected :it :any ii'istunt in shunty nhoutl the corresponding mechunisrn B, is decreased or increased :is the .steunt pressure rises and frills, hy means ot' :i con tact plute M to which the conductors 24 are connected and which is carried by the free ends of n. pair of Bourdon tubes N to which the steam pressure is transmet-ed through the pipe N. This special construction is not claimed specifically herein as it is disclosed and claimed in my copending appliution, Serial No.. 499,403, tiled Septemher 9, 1921. lt will he obvious to those .skilled inthe nrt that the vuriable. resistentes (lf muy euch he connected in series with the, eorresmnding conductors 15 and 16 instead of in thev .shunty thereto as illustrated, but. when connected in series, the ortions of resistzinces G7 in circuit should eerease and increase as the steum pressure decreases and increases. v

ll'ith the apparatus shown in Fig. 1, the boilers having their combustion regulating devices B connected to' the steady load bus hars 1.7 und 1R. will have thex bustion automatically increased and decreased ns the steam pressure falls and rises :ihove normal, and with suitably designed apparatus, a very effective' control of the rate of combustion muy be, had in this man ner. In general, when the only automatic control of the rate of combustion is in ref spouse to steum rassure, sisit would be when operating with the switchy J open as nhove described, the pipe Nshould he cennected to the steam mein at some distance from the boilers so that the, pressure would he :1 compound function of" the pressure at.y

the hoilers, und the drop in pressurelietween the boilers und the pointlofconnection so that said drop in pressure would increase or deereuse with thene of steam flow.

Those skilled in the. art will, understand that the control system dingfiuminaticslly illustrated in Figi. 1 is well n opted for its intended purpose, of accurately regulating conilnistion conditions in each of a. battery of boiler furnaces from :i single switchboard or control station. The viirious meters provided make it. possible to observe 21nd. if these meters are recording meters, to record the performance of each individual hoiler. The flexibility of the control system permits of any desired change in operating condi`4 tions. For example, it permits of changes :it will in combustion conditions in the luit-N tei.) es u whole, or in :my individuel looiler furnuces which muy he desired in practice. If one of the steam outlets C and (1 is closed. und the corresponding How balance D or 1M if.' thereby rendered inoperative, no chung-e in the control sii-stem as a Whole would. he required. suie possibly an adjust nient of the switch lewe: g', und an udpistment ol' the rheostet G.

ln the euse ot any holler having "s control ,nieclninisin B energized from t steady loud hns hars 7 :ind 18, the contri, the

rute. ol' conihustion in the boiler ini.. he purely meinuiil` sure as itr is modilied hy i. i control provisions responsive to steam pressure, which muy he dispensed with in some cases; while n boiler rate of combustion is 1r rates of com-.

'sally in Fig? ,Lt represents a. boiler furnace adepti io be heated partly by the crnnhustiou of one fuel, as blast furnace gas, r-.rniiiphmi "through the conduit l at a rati which dues not vary with the heat requirement of .ne furnace and which is insutiirieut :no tally supplythose requirements, and pa `u f the combustion ot another incl. as ii'maifiered coal. which is supplied through a conduit ti as required to furnish ilu` additif" heat needed. Associated with the furnace fit/l1 are control provisions for rewulfiing; the toed ot' powdered coal {its} air required for the combustion e reu! .il toet and gas, which proi y. may he regarded as to one olf the control mechaif. 1, and are adapted to be controlled by a correspondinir ir o1 the ocal control conductors 15 :mtl iti of lig). l.

'The f onrol provisions shown in Fig. 2 compr, ttor.' l'ialances DP, DQ, and DS, anale special balance Dlt. and other parts and circuit rounmftions' hereinafter referred te. The Stow haianre lll) may be identical i with the master flow balin consti urt arises4 D mit D. of Fig. l. but preferably i @lille/reu? type of differential sach as that shown iu which in a sealingr liquid is susi u arni ot the lever D2. lll* operate.` through a rheofis ierciwilile actuating motor 1 i current' tlow through the 'fri including the coils D and i Dl and DQ, and conduclurh is proportional to the :ww to the furnace through the conduit ff. This circuit portion is connected betweeshe control conductors 15 and tti. The ilor balance DQ. which is similar in oom :zx-fion to the hala'ice D1) operates :aff :'H'ersihle motor FQ to open valve or damper U in an air wi'iftwt Q as required to malte the .iw lf: the furnace through that conthe4J f '.onai to the gas flow through tie coed' f il'. I'lhe portirri of the current hr-iv.':--: u the roiuluctors lil and 16 which i s not pass turougl'i the coils of the balences DP and DQ, passes through a Cucuit portion comprising conductors Q7 and ze and the balance coils D* and of a. flow balance DS and of a specia1 ball' ance Dlt.

The balance DS, which may be identical in construction and general purpose with the balance Dl, acts through the reversible motor FS to adjust a damper U in the air' supply conduit S as required to make the rale at which air is supplied to the furnace by the conduit S, proportional to the strength of the electric control current passing through the coils of the balance.

The purpose of theI special balance DR is to make the rate at which powdered fuel is supplied to the furnace through the conduit R, proportional to the strength of the electric currentflowing through the coils D and D" of the balance. The balance DR diil'ers from the various flow balances in that the balance lever D which carries the floating coil D, is not acted on by a differential pressure gauge, but by the diaphragm or flexible wall portion of a pressure chamber D, in which a pressure is maintained which is proportional to the square of the rate at which powdered coal is passed into the turnace through the conduit R. For this purpose the motor R2 which operates the powdered coal .feeding device R', also operates a small compressor R"r which has its outlet connected to the chamber D, and thus maintains a pressure in the latter proportional to the square of the speed of the motor R2. The speed of the motor lt2 is regulated by a controller R3 which is adjusted by a reversible motor FR. The motor FR is directly controlled by the* balance lever Dl through its switches E and E. and acts to speed up the motor R2, or to slow it down as required to maintain a balance het ween the yforce exerted on the lever D by the yelectromagnetic interaction of the coils D4 and D5, and the force exerted on thc lever by the flexible wall or diaphragm of the pressure chamber D. The various reversible motors FP, FQ, FR and FS may be similar in c011- structiou and mode of operation to the motor F associated with the master flow controller D, and the two energizing conductor connections from the supply conductors l and 2 to each of these motors are designated b v the symbols 6 and 7. l,

It will be understood that in the contemplated niode ot operation of the apparatus shown in Fig. 2. the total current flowing through the conductors and 16 is a 1neas ure ot the rate at which heat is to be supplied to the boiler furnace AA, and may be supplied from the bus bars 12 and 13, or trom the bus bars 17 and 18, orl directl from the supply conductors 1 and 2,throu the conductors 19 and 14 of F ie'. 1. o1'. .int e manner illustrated in Fig. 4. The flow balance D through the rheostat GP con trolled it, divides the total current into two portions, one of which varies with the 6 rate of vas flow through the gas supply conduit l), and through the balance DQ controls the supply of air for combustion of the gas passing to the furnace through the conduit Q. The other portion of the IU control current acts through the balances DR and DS to supply powdered coal and air for its combustion, as required to sup ply whatever heat is needed in addition to that furnished by the combustion of the gas supplied by the conduit- P, to make the total heat supplied to the furnace propor- 'tional to the total control current flowing through the conductors 15 and 16.

To avoid unfavorable combustion conditions and the possibility ot explosions in a furnace heated by the combustion of powdered coal, it is desirable on any increase in the rate ot combustion to increase the supply of air supporting combustion at a rate more rapid than the rate at. which the cuit of the motor FR, which acts when closed to sped up the motor R2. The etliect of this is to retard the speeding up of the motor R2 on an increase in the control current tlowing through the coils of the balances DR and DS as compared with the rate at which the motor FS increases the rate of air supply by adjusting the damper ll. It it is also desired to retard the rate at which the supply of air is diminished. in comparison with the rate at which the motor R2 is slowed down. on a decrease in the current passing through the balances DR and DS. that result may be obtained by placing a resistance t/k as shown. in that energizing circuit of the motor FS which is closed to bring about a closing movement of the damper U.

lt will be understood. ot' course. that in lieu of the special external resistances .f/o and y". the ditlereut windings ot the motors FR and FS may be specially formed or proportioned .to retard the acceleration et each motor in the one direction in which its motion should be retarded to increase the air to fuel ratio during periods in which the rate of fuel supply is being varied.

Instead of utilizing master flow balances such as the balances D and DA. to maintain a control force varyiner with the total load on the various boiler urnaces. other means for creating a control force proportional to the total load may be employed. For eX- ample, as illustrated in Fig. 3, when all or approximately all of the steam generated is used in driving a prime mover or prime, movers operating electrical generators. thc, electrical energy generatetl is an approximate measure ot' the boiler furnace load. and may be utilized to create a control torce tor operating a control system such as that illustrated in Fig. 1, and in Fig. $3 I have illustrated an arrangement of this sort.

In Fig. l the boiler furnaces A'. .U and A3 are all shown as delivering steam through a common steam main (T. to a turbine Z driving an alternator ll' furnishing current to the supply conductors 2S() and ttl. liz-- cludcd in series with the supply ctmductm's 4U is the primary coil X ot a current transv former.v the secondary coil X. ot which is connected to terminals ot' the switch J. and when the latter is closed. supplies current to the variable load bus bars 12 and 12.. The primary winding Y of a constant potential transformer is connected across the couduc tors 3() and 40. and the secondary winding Y of this transformer is connected to tbc terminals of the steady load switch l.. so that when the blades of the switch lA arc iu their lower closed positionthc steady load bus bars 17 and 1S are directly connected 'to the terminals of the secondary winding Y. while when the blades of the switch ll are in their upper closed position the bu;-4 bars 17 and 1S are connected to the terminals .f1-t the secondary coil X ot the constant cui rent transformer. in series with a currcnt regulator X2 otl any usual or suitable tot in for maintaining a constant rate ot current flow to the bus bars 1T and 18 from the secondary coil X. lu consequence. wbcu the Switch blades of the switch ll are in their upper closed position. and the switch .t is closed, tbe current supplied to the .ariable load bus bars L?. and I8 will be less than the current which would be supplied to those bus bars if thc switch L were open. or had its blades in their lower closed position. by the amount of current then being lsupplied to the steady load bus bars 1T and 18. Associated with the control system shown in l"ig. fl are ammcters HB. il@ and lll) for showing the current tlow in ditl'cr ent portions of the control system and advantageously ct'indensers 100 are provided for maintaining a proper power factor in the control system. The specitic torni ot my invention illustrated in Fig. El forms they subject matter otl my divisional application Serial No. 728,344. tiled July 26. i924.

In the arrangement. specifically illustratetfi in Fig. 1. when the blades of the switch it are in their lower closed position, and the steady load bus bars 17 and 1S are than utilized in bringing one or more boilers np to the working pressure, it is not possible to operate any of the boilers then in service under constant load. Whe-n, as may be desirable in some large stations having many boilers operated from the same control system it may be desirable to operate one or more boilers at constant load while simnl` taneously other boilers as required to supply the balance of the plant steam requirements, and at the same tune maintaining a steady .rate of combustion in one or more boilers being heated up and not et delivering steam, I may advantageousy employ the modification shown in Fig. 4.

The apparatus shown in Fig. 4 differs from that shown in Fig. 1, in that the steady load switch L is dispensed with, and the steady load bus bar 17 and 18 are constantly energized by direct connection to the conductors 2() and 14, respectively, of Fig. l. Associated with the local control circuit conductors 15 and 1G of each of the different boiler`furnaces is a corresponding switch LA', LA2 and LA3, by which the conductors 15 and 16 running to the control mechanism `of any one of the different boiler furnaces A', A2 and A3 may be connected directly to the supply conductors 1 and 2. lVith this arrangement, for example, if the switches LA2, LA8 and K are open, and Ihe switch LA closed, and the switch K2 has its blades in their upper closed position. and the switch K3 has its blades in their lower closed position. a stead)v rate of combustion Will be maintained in the boiler furnace fi" as required to heat up that boiler furnacYY preparatory to putting it into service. the boiler furnace A3 will operate under constant load, and the boiler furnace A2 will operate under a rate of combustion varyingr with the difference between the total load and the portion of the load carried by the boiler furnace A3.

While in accordance with the provisions of the statutes I have illustrated and described the best forms of my present intention now known to me. it will be apparent to those skilled in the art that changes may be made in the form of my invention without departing from the spirit of m); invention as set forth in the appended claims, and that certain features of my invention may sometimes be used to ad 'antage Without a correspondingT use of other features.

Having: now described my invention` wh at I claim as new and desire to secure by Letters Patent, is:

1. The method of autonuiticall;7 regulatingr combustion in a plurality of boiler furnaees supplying steam to a oon'imon dis tributing system having a pluralityY of outlets, which consists in establishinsr a control force proportional to the steam flow through each of said outlets, and varying the aggregate rate of combustion in said boiler furnaces in response to variations in the sum of said control forces.

2. The method 'of regulating combustion in a batteriY of boiler furnaces which consists in maintaining a control force proportional to the total boiler load, dividing said control force into portions one 0f 'which is a constant quantity, utilizing said constant quantity to maintain a steady rate of com bastion in one or more of the boiler furnaces, and utilizing the other portion of the control force to maintain a `rate of comhustii'm in the other boiler furnaces which varies with the portion of the total boiler load not borne by the boilers operating with a steady rate of combustion.

3. ln the method of claim l, the further step which consists in varying the rate of combustion in the various boiler furnaces in inw-,rse response to changes in the pressure ot' the steam `generated.

4. The method of automaticalliy regulating combustion in a furnace heated by the combustion of fuel supplied from two separate sourcesv` which consists in creatingr a control force proportional to the total rate of heat generation desired in the furnace, diminishinf.T said force by an amount proportional to the rate at. which fuel .is supv` plied from one of said source* and utilizing; the remaimn;rl portion ofsaiil l nwe tu regu. late the supp; of fuel from the other scm'ce.

The meihcd of operating! a furnace lit-ated b v ihr combustior of pou which consists in autonnitiealtr u a prede!Hrnined ratio between tluf'rates at which the powdered furl iin-:l air for it?A combustion are supplied to the furnace div ingr periods in .rln the rate of nel supply is substantially uniformA :intl auli'imatiically inert-anfing the ratio of air o fuel supply during" periods in which the ranof fuel supply is changing.

il. The method of operating a furnace heated bjr thc combustion ol' powdered fuel which consists in automatically maintaining a i)redeterrziincd ratio between the re '1 at which the powdered fuel and ai mi' its voinbustion are supplied to the. ,furnace dur ingr periods in which the rate of 'luci supply is srlretantiall;Y uniform., and automatically increasing' the ratio of air to fue lurinf if-riode in which the rate of fuel supply is lining' increased 7. lhe combination with a batters' of boiler furnaces and a separate electrical ron trol mechanism for each furnace. for regu latin;r combustion conditions therein, of an cle'trical control system comprisiner steady load bu:` bars. rariable load bus bars, proisions` for optionall`7 connecting each of said mechanisms to the sternly ioad ons ha rs or to the variable. load bmv bars. ni -ans for maintaining` a conf-:tant potential difference between the steady load has hars, and means for maintaining a potential difference between the variable load bus bars varying automatically with the dilference between 'iti 'lli

the total boiler load. aud the portion ol' that load horno h v the boilers operatingr from the steady loud liu.: oars;

The eonibiuaiion with a battery ot' boiler furnaaes and an eltwftrically controlled eoiubustion regulatingr mechanism for carl: boiler, olA a t'onirol system osuA prising' one or more rlertrir llow balanrcs responsive to the strani output. ot said furnaces. :nonna tor passing a rouslaui balanc` ing;t rurrent through .said balances to eruh olone or more ot said control tuorli-.anions to maintain a ron tant rate ol combustion in the oorrcsiminding holler tornare or lurv naoes, and means auioniati ally aojusled by the halanees for passing a rurrent through said balantes lo the routrol iii-.'r'luinisuis ot' the other furnafes. which varies as required to malto the total rui-rent limi' through the balances proportional to the total steam neration ot the boiler turnares.

9. The combination with a battery ol" boiler furnaces and a selimrate eontrol mechanism for earh t'urnare t'or regulating combustion ionditionsI therein. ol provisions controlling somo ot said mechanisms as required to maintain constant rates ot' oomhustion in the corresponding furnaces, and provisions cmitrollingother mechanisms as required to malte the correspoudiiig boiler terneros operate with a rato of combustion proportional to thel difl'erenre between the total boiler tornare load and the. portion of that load borne by the boilers fontrolled by the lirsl, mentioned provisions.

1t). The combination with a battery of boiler furnat'es and a separate control nierhanisni for eaeh furnace for regulating;V eonibustiim rouditionf; thereinr` of provisions controlling.;` said mechanisms as reiipiired to maintain lconstant rutas ol "oinbustiou in the correspondinrr furnaces, i/rovisions for eontrolling Said nietflninisins as required to make the correspondirp boiler '.unaees operate with rates oi' -fonfiusliig-u proportional to the dillerenee lietifeei'i the total boiler furnaee load and the portion ot' that l load `borne by sueh oi' the boilers as are then eontrolled by the, first mentioned provisions. :ind means tor optionally suhjevting ear-h ot' said mechanisms to the eonirol of either ol` said provisions.

ll. The combination with a lisitteiy of boiler furnaces and a separate eleetrif-:i :ontrol tnethanisni tor eaoh turner@ for retin latino the eoinbustion ronditlons therein. ofV an electrical control syst/:ini ifoiuprif'injf, variable loud bus bars. steady load bus ha s, u urli inerliauisui foi optionulh connecting i irh o' :41nd control mei h snis to the sup pix f-oinlurlors` lo the, variable load beu: hars or to the steady load bus bars. means, for niaintaii'iing a poteftal fiill'rrenee betreten the variable load hof .liars proportional to the total load ou the boilers controlled l rom the variable loadv bus bars and means for maintaininpr a constantI potential difference between the steady load bus bars.

it. The eoinhinaiion with a battery olt boiler furnaces and a separate elertrieal control mechanism for each furnace l'or regulalinLr the iomhustion conditions therein, of an elertrical rontrol system compris-ingr supply conductors. variable load bus bars, trudy load bus` hars. switch mechanism for opiionaly connertinp' each oll said control nicrhauislns: lo the supply eo11dut'tors.tothe variable load bus bars. or to the steady load bus bars. means tor maintaining an cleoA4 [rival control rurrent flow proportional to the total load ou the boilers, and means for passing; .i ronstant portion ot' the control current tlow through the steady load bus bars to Ihr` mechanism connected thereto, and lor passing the remainder of the current tiow throinrh the variable load bus bars to the mechanism eonnetted thereto.

ll. 'lhe combination with a plurality 0f boiler furnaces supplyingr steam to a eoni mon distributing system provided with a plurality ot steam outlets, of means assoriated with each outlet for maintainingr an elet-tric current tlow proportional in strength to the steam flow through said outlet, and moans responsive to the aggregate strength otl said control currents for varyingr the ag greg'ate boiler furnace rate of combustion in proportion to said aggregate strength.

M. The t'ombinatiou with a plurality of boiler furnaces supplyingjr steam to a coninion distributing system havin;v a plurality ot' outlets. ot' means associated With each outlet tor maintaining a Control force proportional in strength to the steam flow through said outlet` and means actuated by said torres tor varyingr the aggregate boiler furnace rate ol' eoinbustion in proportion to the. stun of said t'orces.

l5. The ronihination with a` furnare heated by the eonilulstion of powdered (foal, ol' means responsive to the rate at which powdered eoal is supplied to the Jfurnace, means responsive to the rate at which air l'or the combustion oi" the coal is supplied to the Vfurnace. and iontrol provisions notuatod by said means and tending to maintain a constant ratio ot" air to roal supplied when the ra e ot 'goal supply is approximately 'constant and to inerease said ratio duringr periods in which the, rate, of 'oal supply is increasing.

lll, 'l`hf.` combination with a heated hy the eonibuslion of powdered Coal7 ot means responsive to the rate at Vwhich pondered eoa.' is supplied to the furnace, means responsive to the rate at which air l'or the combustion ol the eoal is .supplied the furnace. and control provisions aetu 1f- .l by said means and tending` to maintain a eonstant ratio of air to coal supplied when furnace,-

lll)

the rate of `430:11 supply is approximately inverse responso to changes in the pressure constant and to ,im-rieuse said ratio during of tho strani gom-rut-od.

periods in which the rato of voui supply is Signwl :it Now York, in the county of l0 varying. Non Yori( and Sinto of Now York, this fir l 17. In tho method of claim 2, the furtlior day of Maw-h A. l). 1923.

,smo whiiix ronsists in varying`r thv rute of mmbustion in the various boilm' furnacvs in GEORGE II. (lSUlN'. 

